The present application is based on and claims priority from Japanese Patent Application Hei 11-201064 filed on Jul. 15, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a stator arrangement of a vehicle AC generator for a vehicle.
2. Description of the Related Art
GB 2202170A discloses a stator winding of an AC generator. The stator winding has in-slot portions which has rectangular cross-section to be inserted into slots having parallel walls and circular cross-section at other portions including coil-end portions. This structure is effective to provide a stator winding of a high space factor.
Generally, heat generated in a stator winding operation is conducted to a stator core from slots and to a frame. Therefore, temperature at the stator winding is higher than temperature at the stator core, which is higher than temperature at the frame. Because copper of the stator winding has a 40% higher thermal expansion coefficient than iron of the stator core, the portions inserted into the rectangular slots disclosed in the above patent may receive huge pressure from the walls of the slots due to the difference in thermal coefficient between the stator winding and the stator core, especially while the rotor runs at a high speed at which very high frequencies of the output power is generated. This may break insulators disposed between the stator winding and the stator core, because the stator core is a lamination of press-formed steel plates having burrs.
A main object of the invention is to provide an improved stator arrangement of a vehicle AC generator.
Another object of the invention is to provide a reliable stator arrangement that can restrain temperature rise at a high speed range of the rotor.
In a vehicle AC generator according to a feature of the invention, a rotor has at least 16 claw pole pieces and is rotatable at a speed where a multi-phase stator winding generates AC output power at a frequency of about 2.7 kHz. The multi-phase stator winding is comprised of a wire having a minimum width equal to or less than 2.6 mm, and insulators and the winding are disposed in close contact to each other between parallel walls of slots.
The winding of above vehicle AC generator preferably has rectangular in-slot portions conforming to the parallel walls of the slots.